This invention relates to radioactive microspheres that may be used to locate and irradiate specific targets within the body of an animal or human. More particularly, this invention relates to the use of a microsphere core coupled with a chemically prepared polysaccharide to which is attached a specific targeting molecule. As these spheres may also be combined with non-radioactive drugs, they can be applied to a wide variety of other uses in specific site detection with non-invasive imaging equipment (such as magnetic resonance imaging) and can be used to remove specific molecules, viruses or cells from the circulation.